"The search area remains the same, but some of the information that we now have suggests to us that areas a little further to the south -- within the search area, but a little further to the south -- are of particular interest and priority in the search area," he said.
His comments came as Australia and Malaysia signed a memorandum of understanding in Canberra over the next phase of the hunt for the plane, which disappeared on March 8 with 239 people on board.
It is believed to have crashed into the southern Indian Ocean far off the west coast of Australia, but a massive air and sea search failed to find any wreckage while an underwater probe gave no answers.
Experts have now used technical data to finalise the most likely resting place of the plane deep on the ocean seabed and are preparing for a more intense underwater search, beginning next month.
It will focus on an area of ocean measuring 60,000 square kilometres (23,000 square miles).
Truss said investigators still believed the aircraft was resting somewhere on the search zone's seventh arc, where it emitted a final satellite "handshake".
"It remains on the seventh arc -- that is, there is a very, very strong view that this aircraft will be resting on the seventh arc," he said.